The scientific and technological interest in miniaturized humidity and chemical vapor sensor devices has grown in recent years. The need for such sensor devices spans a wide range of industries and applications, such as the medical instrumentation, food and agriculture, paper, automotive, electric appliance, petrochemical, fuel cell, and semiconductor industries, as well as the military, in, for example, humidity, chemical vapor, organic vapor, and gas sensing applications. The wide range of environments that these sensor devices may be exposed to severely limits the candidate materials that may be used to build the sensor devices. A number of humidity and chemical vapor sensor devices have been developed and built for specific applications. However, none of these sensor devices demonstrates a suitable combination of the desired robustness, sensitivity, selectivity, stability, size, simplicity, reproducibility, reliability, response time, resistance to contaminants, and longevity. Thus, what are still needed are humidity and chemical vapor sensor devices, among other sensor devices, that exploit the high sensitivity of the magnetostrictive resonance frequency of soft magnetic thin films to changes in mass and the unique properties of certain porous nanostructured thin films, nanoparticles, nanorods, nanotubes, and nanofibers, including their high adsorption potential, high adsorption rate, high desorption rate, high chemical stability, and heat release characteristics associated with the physisorption of water vapor and chemical vapor molecules.